The production of stable, aqueous dispersions or solutions of plastics is known from the prior art.
Thus, the production of aqueous dispersions or solutions of polyurethanes which may contain urea groups is described, for example, in German Pat. Nos. 1,178,586 and 1,184,946; German Offenlegungsschrifts Nos. 1,495,745, 1,770,068, 2,314,512, 2,446,440, 2,543,091 and 2,642,073; U.S. Pat. Nos. 3,480,592, 3,388,087, 3,479,310, 3,756,992 and 3,905,929 and in "Angewandte Chemie", 82, 53 et seq. (1970).
The production of aqueous or water-dilutable polycondensates, particularly polyester resins, which may contain organic solvents and urethane groups is also known from the prior art (cf. for example German Offenlegungsschrift No. 2,225,646, German Auslegeschrift No. 2,239,094, German Offenlegungsschrift No. 2,446,439, U.S. Pat. Nos. 3,876,582 and 4,029,617 and also Houben-Weyl "Methoden der Organischen Chemie", XIV/2 (1963), pages 30 et seq).
The production of polymers, particularly polyacrylates, containing incorporated ionic groups is also known from the prior art (cf. for example Houben-Weyl "Methoden der Organischen Chemie", Vol XIV/1 (1961), pages 1033 et seq or XIV/2 (1963), page 754).
All processes for producing dispersions or solutions of the type in question are based on the principle of incorporating hydrophilic centers into a macromolecular chain of a polymer. In the known dispersions, these hydrophilic centers, or so-called internal emulsifiers, are ionic groups or ether functions. These centers are generally introduced either in the form of special diols or in the form of modified amines during synthesis of the polymer.
In the case of cationic aqueous systems, a basic nitrogen atom is generally incorporated in the polymer chain, being converted into the salt form by quaternization or by neutralization with an organic or inorganic acid.
Unfortunately, known cationic dispersions are frequently attended by serious disadvantages. On the one hand, the ionic groups remaining in the polymer can seriously affect its wet strength. On the other hand, the inorganic or organic acids which are liberated during stoving or their corrosive decomposition products frequently destroy the coating or dipping units used for applying the dispersions by corrosion. Hydrochloric acid and acetic acid are particularly troublesome in this respect.
An interesting solution to this problem is proposed in German Offenlegungsschrift No. 2,460,470 (corresponding to British Pat. No. 1,523,739), according to which the basic nitrogen atom is converted into the salt form in aqueous phase using carbon dioxide and is used in this form as emulsifier for the polymer.
However, this process is attended by two serious disadvantages.
1. It is necessary to use powders or organic solvents for homogeneously dissolving the polymer, and
2. the dispersions formed show only very limited stability in storage because of the weak acidity of the acid used. Dispersions produced by this process sediment after a few days.
An object of the present invention is to provide storable dispersions or solutions of cationic polymers which lead to ion-free, hydrophobic, i.e. water-resistant, coatings and bonds.
The present invention provides for the first time storable aqueous dispersions or solutions of ionic plastics which, on heating, i.e. during and/or after application of the dispersion or solution, lose thier ionic character without corrosive acids or other decomposition products being released at the same time. The new principle according to the invention consists in converting oligomeric or polymeric plastics containing tertiary nitrogen atoms into the water-soluble or water-dispersible salt form with acids, which, on heating, lose their acid function without releasing corrosive decomposition products or in using low molecular weight synthesis components containing ammonium groups obtained by reacting tertiary amine functions with acids of this type for the synthesis of the plastics.